here we are on the Stored Product Insect page...these are, in most cases,
very small insects which infest products like grain, flour, cheese,chocolate
etc..etc..etc,(and I don't just mean in packets..I'm talking in thousands
of tons). People who are not in the industry of food production or pest
control never really realise what a battle is fought to make sure that
the products which come to you are just the product with no added protein
(ha-ha). Food factories, bakeries, supermarkets, suppliers, farmers,
breeders, the list goes on and on, all are bound by the Food Regulations
and Environmental Health to ensure that the environment they produce
their product in is the cleanest and most hygienic possible. One of
the main aspects of this regime is pest control.
many of the products used in this country are of course imported, hence
there are very strict regulations governing the risk of also importing
pests along with the product. In the case of containers these are fumigated
with gas (depending upon the goods).
Let us get one thing quite clear for those who do not work in the pest
control or food industries: Fumigation is the use of a gas (not the
spraying of insecticides) to destroy pests which may infest a building
or a product, an item of furniture, a car in fact virtually anything
can be fumigated, there are exceptions but generally this is the case.
Let us look at a quick example:
a customer rings up and says that they suspect that they have woodworm
in a beautiful regency sideboard, can we do anything to help, will it
damage the item, etc, etc. Well yes we can help and we go along and
pick up the item, take it to our gas chamber, or conversely we can seal
it into what is called a "stack", which is parcelled up in
heavy gauge polythene. Once we are sure that everything is gas tight
we can calculate the volume of the stack or chamber and thereby calculate
the dose of gas required (there are different doses for different pests
at varying temperatures) and introduce it, this is a skilled job and
can only be carried out by highly qualified personnel.
are various gases which can be used these are:
Methyl Bromide (CH3Br) supposedly to be phased out by 2005 (possible
(2) Nitrogen (N2)
(3) Phosphine (PH3)
(4) Carbon Dioxide (CO2)
back to our example. The item is left under gas for a certain time period,
this varies with which gas is used, in the case of methyl bromide used
on woodworm it can be 48 - 72 hours, if it was done with carbon dioxide
it can be 2 or 3 weeks. Anyway, once the required time period has elapsed,
the qualified personnel then return and vent off the chamber or stack,
that is let the gas out, and using various instruments, determine when
the item is free of the gas and able to be returned to the customer.
thing about fumigation is that it isn't residual...it will kill the
pests in the item and it will also kill the eggs, which spraying doesn't,
but it does not leave a barrier to protect against re-infestation.
in the case of a grain store of food factory etc, if there were a need
to use fumigation, it should be used in conjunction with a spraying
program and the situation should be closely monitored. I'm all for using
pesticides if it is needed, but only in the absolute necessary amounts,
and not bucket-fulls, this is why monitoring is needed so that only
the areas which need treatment get it.
Aspects of Fumigation:
are low molecular weight chemicals, highly toxic and volatile, that
are used during storage to kill all insect stages residing in the produce.
Fumigation is a widely used method all over the world on small as well
as large storage scale. The method can be applied at the farm level
in gas-tight granaries or silos, under gas-tight sheets carefully covering
the product or at a large scale storage as in large warehouses.
are commercially available in a solid, liquid or gaseous state. Phosphine
(PH3), for example, is a formulated fumigant commercially
available as either tablets, pellets, bags or plates. Methyl bromide
(CH3Br), on the other hand, is gaseous in form and packed
in a liquid form in pressurised steel bottles. At temperature above
40°C it takes a gaseous state, thus, once the container
is opened, the gas is released and starts to act as a fumigant. The
two compounds are the most widely spread fumigants in use.
a problem of human toxicity due to inadequate application of the method
is considered a drawback regarding this industry, specially in the developing
countries, where inappropriate handling of such toxicants is widespread.
Another problem with the use of fumigants has recently aroused, which
is the developing of resistance from insects against fumigants. The
problem started as a result of improper application of the chemicals
in use, i.e. application of incorrect doses, fumigation in non gas-tight
containers or insufficient exposure time. Recently, fumigation has been
highly discouraged at a small-scale level. moreover, the use of methyl
bromide has been strongly restricted in industrialised countries because
of its ozone-depleting potential. However, fumigation is still the most
widely operated method as an essential large scale post-harvest practice.
search for other alternatives
have been conducted on the use of carbon dioxide as a fumigant to replace
methyl bromide in the control of insects and mites damaging stored products.
The use of CO2 rich atmospheres showed promising results in disinfesting
food commodities in small storage facilities. A relatively new technique
used by the Indonesian National Logistic Agency (Bulog) for milled rice
is to seal bag sticks into large plastic enclosures flushed with carbon
dioxide (Hodges & Surendro, 1996).
with high-pressure carbon dioxide under different temperatures may result
in different rates of mortality, for example, at 15°C,
95 percentage mortality of Lasioderma serricorne was observed
after 38.5 min of treatment, while the same level of control was achieved
within 1 minute at 45°C (Ulrichs, 1995). Corinth &
Rau (1990) showed that each tonne of grain requires about 19-27 kg carbon
dioxide to achieve complete mortality of Oryzaephilus surinamensis,
Tribolium castaneum and Sitophilus granarius
in 4-6 weeks.
use of "Biogas" as a fumigant, with methane and carbon dioxide as its
main components, may achieve good results in the control of stored pests.
Subramanya et al.(1994) showed that biogas significantly reduced
infestations and loss in stored pigeon pea infested with Callosobruchus
chinensis. Gursharan et al. (1994) recorded up to 100
percentage mortality of Sitophilus oryzae, Rhyzopertha
dominica, Trogoderma granarium and Tribolium
castaneum after six days' exposure to biogas in PVC bins. Another
method for the control of insects in industrial premises was developed,
where a Gas Operated Liquid Dispensing system was used to mix separate
sources of carbon dioxide and insecticide concentrate. The system, given
the name Turbocide GOLD, produces a fine insecticidal aerosol that was
reported to give excellent control of Tribolium castaneum,
T. confusum and Lasioderma serricorne (Groome
et al., 1994).
studies have focused on developing post-harvest technologies as a key
role in ensuring food security. Consumers are now aware of the danger
in the use of chemical pesticides to protect stored products. This,
and the world-wide trend to minimise the use of toxic substances applied
on food products, have led scientists to seek less dangerous alternatives.
Fumigation, for example, has become an endangered technology due to
pressures regarding environmental contamination and health concerns.
problems, then email me by clicking on the Piedpiper below:
Stuart M Bennett 2003